Push-pull cable casings



Aug. 6, 1968 J. F. MORSE PUSH-PULL CABLE CASINGS 2 Sheets-Sheet 1 Original Filed Oct. 2, 1962 .bm KORE INVENTOR JOHN R MORSE BY M AT TORNE YS Aug. 6, 1968 J. F. MORSE PUSH-PULL CABLE CASINGS 2 Sheets-Sheet 2 Original Filed Oct. 2, 1962 INVENTOR. JOHN F. M OR ATTORNEYS United States Patent 3,395,551 PUSH-PULL CABLE CASlNGS John F. Morse, 21 Clinton St., Hudson, Ohio 44236 Original application Oct. 2, 1962, Ser. No. 227,889, new Patent No. 3,320,665, dated May 23, 1967. Divided and this application Dec. 6, 1966, Ser. No. 620,197

5 Claims. (Cl. 64-3) ABSTRACT OF THE DISCLOSURE A casing for push-pull control cables in which a plurality of casing wires are laid side by side in a long pitched, helically spiraled coil around a flexible, plastic inner tube. The radially inner surface of each wire is embedded within the inner tube, and, at random intervals, the material forming the inner tube extends radially outwardly between the adjacent casing wires to anchor the inner tube against substantial longitudinal movement with respect to the casing wires. A flexible, outer covering encompasses the coil of easing wires such that the radially outer surface of each wire is embedded therein. The embedment of the casing wires into both the inner tube and outer cover eliminates voids and interstices between the casing components.

This application is a divisional application of my prior copending application, Ser. No. 227,889, filed on Oct. 2, 1962, now U.S. Patent No. 3,320,665.

The present invention relates generally to push-pull control cables. More particularly, the present invention relates to flexible control cable casings adapted to receive a flexible core slidable therein for transmitting mechanical motion in either direction when the casing is clamped in position.

The push-pull cable, generally, is well-known to the art and it is the purpose of the present invention to improve upon the construction and method of manufacturing the outer casing.

Although the prior art shows many constructions for push-pull control cable casings, one of the most suitable constructions to assure greatest flexibility and efiiciency comprises a plurality of wires laid contiguously in a long pitch helix around the outer periphery of a plastic tube. The helically arranged wires of the casing are maintained in their proper position solely by a plastic cover in the smaller cables and by a reinforcing spread helix of wire or flat metallic ribbon, in conjunction with the plastic cover, in larger cables.

The plastic tube which comprises the innermost e1e mentof the cable casing acts as a bearing for the core of the cable which is slidable within the casing and also acts to protect the casing wires from the elements having access to the interior of the tube. The plastic cover, which comprises the outermost element of the cable casing, not only acts as a structural member to retain the casing wires in the coil shape but also acts as a protective member to shelter the wires from the exterior elements.

Fittings are provided at each end of the cable to provide a means for securing the control cable in operative position and to seal, as well as possible, the ends of the wires from the elements. To be completely effective, an end fitting must cooperate with the interior tube and the outer cover. However, because the reciprocating action of the core within the casing tends to act as a pump and futher because the prior art means of effecting a seal between the end fitting and the interior tube are generally unsatisfactory, the cable, when used in such exposed applications as with outboard motors, is subject to the entry of water from either or both ends of the cable which finds its way to the wires. Stainless steel and other noncorrosive metals are not satisfactory to provide the spring temper requirements of the wire which makes the best casings, so that the wires which are used are quite subject to rust, especially when subjected to salt-water exposure.

Nor would this corrosive action be limited to the ends of the wire in the cable casing. Because of the aforementioned pumping action, capillarity and/or gravity, once the water reaches the wires it will progress along the wires in the space between the contiguously wound wires and the radially outer surface of the inner tube or the radially inner surface of the outer cover.

With the inception of rust, the adjacent wires seize, or bond, together. This destroys the flexibility of the casing, so that the casing resists bending and will even retain portions of the arcs of previous bends, much like soft metal tubing. Just a few of these sets in the cable casing can easily reduce the efliciency of the cable by 50%.

To fully understand the importance of maintaining freedom from rust, and therefore maximum flexibility, it must be realized that a push-pull cable, at best, is a relatively inefficient mechanism. Some of the best pushpull cables available are capable of only about 50% effi ciency when installed in a boat with an average number of bends between the control head and the engine.

Many outboard motors and some inboard engines or transmissions have high operating loads. Some makes of outboard motors may require as high as 40 pounds to move the shifting lever on the engine under some conditions of operation. This, in turn, even with an ideal in stallation having an average efliciency of 50%, would mean an input cable load at the remote control station of approximately pounds. With a control head having a leverage ratio of 2 /2 to 1, this would result in a hand lever load of 32 pounds. When this hand lever load at the control head is compared to the hand lever load of an automatic transmission in a modern automobile, which might require a maximum of two pounds, it can readily be seen that some marine control systems, even under ideal conditions, may be operating at many times the load that might be considered desirable.

If, for some reason, the efficiency of the push-pull cable system should drop to 25%, the hand lever load at the control head would then be over 60 pounds, which is prohibitively high in terms of safe operation and customer acceptance.

It is therefore an object of the present invention to provide a push-pull cable casing in which the metallic wires are inaccessible to corrosive elements.

It is another object of the present invention to provide a push-pull cable casing in which the inner portion of the circumference of each of the casing wires is embedded in a plastic inner tube and the outer portion of the circumference of each wire is embedded in the plastic outer cover.

It is a further object of the present invention to provide a push-pull cable casing in which portions of the plastic inner tube extend between the casing wires in random location to anchor the inner tube against axial movement relative to the casing wires.

It is a still further object of the present invention to provide a push-pull cable casing as above which facilitates and assures that an effective seal to the end of the casing wire can be accomplished by the cooperation of the end fitting and the inner tube because of the interfitting of the casing wires with the tube.

These and other objects which will become apparent from the following specification are accomplished by means hereinafter described and claimed.

One preferred embodiment is shown by way of example in the accompanying drawings and described in detail without attempting to show all of the various forms and modifications in which the invention might be embodied; the invention being measured by the appended claims and not by the details of the specification.

In the drawings:

FIG. 1 is a push-pull control cable, partly in longitudinal section and partly broken away, according to the prior art.

FIG. 2 is an enlarged transverse section taken substantially on line 2-2 of FIG. 1.

FIG. 3 is a view similar to FIG. 1 of a push-pull control cable employing a cable casing according to the concept of the present invention.

FIG. 4 is an enlarged area of FIG. 3.

FIG. 5 is a schematic representation in cross section of the coiled wires in the casing.

FIG. 6 is an enlarged transverse cross: section taken substantially on line 66 of FIG. 3.

In general, a push-pull cable casing constructed in accordance with the concept of the present invention comprises a plurality of casing wires laid side-by-side in a long pitched helically spiraled coil around a flexible resinous plastic inner tube, as shown in FIG. 6. The radially inner surface, i.e., approximately one-half the surface, of each of the casing wires is embedded into the inner tube so that there are no voids or interstices between the convolutions of the adjacent wires and the inner tube. Furthermore, at random intervals along and about the coil of helically laid casing wires, the material forming the inner tube extends between the adjacent wires to anchor the inner tube with respect to the coil of casing wires so that substantial longitudinal movement of the inner tube with respect to the casing wires is prevented.

A flexible plastic outer covering encompasses the coil of easing wires, the radially outer surfaces of which are embedded therein to fill all voids and interstices between the radially outer convolutions of the adjacent casing wires and the cover.

To assure the desired configuration of the cable casing, the wires are laid onto the tubing and that assembly of wires and inner tube heated sufficiently so that the heat of the casing wire melts the tubing only sufiiciently to assure the desired embedment of the radially inner surface of each casing wire into the tube as the wire and inner tube assembly passes through a sizing die. Immediately thereafter this assembly is cooled to limit the melting of the inner tube to the outer surface thereof. The outer cover is preferably extruded directly onto this interfitted casing wire and inner tube assembly, and an end fitting is secured to each end of any desired length of cable casing in such a way as to effect a seal at the ends of the casing wire between the fitting and both the cover and inner tube. The cable casing is then ready to receive the core.

Prior art In order more fully to explain the advantages derived from the present invention, some pertinent background information on prior art push-pull cable assemblies and the basic problems that have been solved by the prior art cable casings used in these assemblies will be discussed.

The prior art push-pull assembly shown in FIG. 1, and indicated generally by the numeral 10, comprises a core element 11 slidable within a conventional casing, indicated generally by the numeral 12. A plurality of casing wires 13 are contiguously laid in the form of a helical coil having a long pitch about the radially outer surface of an inner, flexible, preferably resinous plastic tube 14 which extends the full length of the casing. The wires are laid to grip the tube 14 sufficiently to prevent relative longitudinal movement between the tube and casing. An outer cover 15 encases the coil of wires 13 up to within a short distance from the end of the Wires 13.

A fitting 16 is fitted over each end of the cable casing and is cold-swaged onto the exposed portions of the cylindrical grouping of wires 13, as at 18. A plurality of angular grooves at 19, within the inner most end of the fitting 16, are crimped down under the cover 15 to effect a seal between the fitting 16 and cover 15.

A recess 20, or other attaching means, is provided on fitting 16 for attaching the cable end to an anchoring point. Generally, an extension tube 21 is swivelly mounted in the fitting 16, as by the socket arrangement 22. Extension tube 21 slidably receives an end rod 23 which is connected to the end of the core 11. Extension tube 21 is closely fitted around end rod 23 to guide the rod 23 and prevent excess deflection of that portion of the core element 11 sliding therein, when subjected to compressive loads.

Sealing elements 24 and 25 are provided at the end of the extension tube 21 between the tube 21 and the end rod 23 and between the tube 21 and the end fitting 16, respectively. While these sealing means 24 and 25 are effective in preventing large amounts of water and dirt from entering the central passageway 26 which extends through the cable casing 12, end fitting 16 and extension tubes 21, the reciprocating action of the end rod 23 and core element 11 has a pump-like action. Thus, particularly when the cable is used in an environment where it is exposed to water as in outboard motor installations, water does find its way into passageway 26.

The plastic inner tube 14 and the end fitting 16 tend to protect the wires 13 from the corrosive action of the water and dirt that finds its way into passageway 26, except at the ends of the Wires 13.

As has been heretofore mentioned, the stranding machine which lays the wires 13 into the helical coil does so onto the inner tube 14 so as to grip the tube 14 suiticiently to anchor it against overall longitudinal movement and yet not deform the cylindrical interior thereof. Because plastic inner tube 14 is pulled through the stranding machine along with the wires 13, and because the tube 14 is somewhat elastic, it Will be retained by the wires 13 in a slightly elongated, or stretched, condition. The cumulative effect of cutting the casing to length, swaging the end fitting 16 onto the wires 13 (which causes the ends to fiare slightly) and the flexing of the cable instant to normal use will cause the squared end 28 of the tube 14 to draw back slightly from the original plane of the cut, allowing a space 29 to form between the end 28 of the tube 14 and the shoulder 30 of the fitting 16 against which the ends of the wires 13 abut.

Because of this retraction of the end of tube 14, the water or other deleterious matter which finds its way into passageway 26 has ready access to the now exposed ends of wires 13. Once the water comes in contact with the ends of wires 13, it will progress along the voids, or interstices, 31 between the radially inner convolutions 32 of adjacent wires 13 and the radially outer surface of the tube 14 because of either the aforementioned pumping action of the end rod 23 and core element 11, capillary action, or gravity. This permits the entire length of the wires 13 to be subject to corrosive action and the attend ant loss of flexibility of the casing.

In an attempt to obviate this destructive result, some cables have been manufactured in which grease has been used to fill the voids 31. So long as the grease fills these interstices 31, water cannot enter. However, control cables are used in a variety of installations subject to wide variations in temperature. When the temperature is high, as, for example, in an engine room, the grease softens and will seep into the very small clearance area in passageway 26 between the core element 11 and inner tube 14. Then, at lower temperatures, this grease in passageway 26 will cause serious drag or even a complete freeze-up of the core movement. This is especially the situation because the radial bearing clearance between the core 11 and tube 14 must be held very close, e.g., in some installations as small as .005 inch, because cable backlash is a direct function of the bearing clearance.

The improved cable casings An improved cable casing made in accordance with the concept of the present invention is indicated generally by the numeral 40 in FIG. 3. The wires 41 in cable casing 40 are preferably oil-tempered, carbon steel, dead-straight spring wires and are laid in substantially side-by-side contact to form a substantially cylindrical grouping around the radial outer surface of a flexible, resinous thermo-plastic, preferably nylon, polyethylene or linear polyethylene, inner tube 42. These wires 41 are helically laid around the tube 42 in a fairly long pitched spiral but, because of normal variations in the straightness of the individual wires, together with the manufacturing tolerances of the wire and tube diameter, the plurality of helically laid wires will not all be positioned in completely touching side-by-side contact. The casing is actually constructed so that if the diameter of all the wires 41 are at the maximum tolerance limit and the diameter of the tube 42 is at a minimum tolerance limit, the wires will lay snugly over tube 42 with a cumulative separation space between the wires amounting to a few thousandths of an inch in smaller cable sizes, and as much as onesixteenth of an inch in the larger cable sizes.

This separation, or spacing, will not occur uniformly between any two given wires 41. In fact, the cumulative spacing will be distributed in random amounts and at random positions around and along the cylindrical grouping of wires.

As shown in FIG. 5, the chain line 44 represents the outer circumference of the circle on which the radially innermost edge of the wires 41 are laid. The individual separation spacings 45a, 45b, 45c, 45d and 45e (exaggerated for clarity) in the summation are equal to the few thousandths to one-sixteenth of an inch explained above. These random spacings will vary, not only around the cylindrical grouping of Wires 41 but also in their lineal disposition along the length of the cable casing.

Accordingly, when the wires 41 are positioned around an inner tube 42, which is constructed to fill the voids and interstices between the chain circle 44 and the radially inner convolutions of successive wires 41, and also extend through the separation of spacings 45a-45e, two major drawbacks of the prior art casings are obviated: There are no voids along the radially inward side of the wires 41 along which water can travel; and, the inner tube 42 is securely anchored against overall movement with respect to the casing wire at the random locations where the key projections 46 are locked be tween adjacent wires.

As is best shown in FIG. 3, the anchoring of the inner tube 42 to the wires 41 prevents even the squared end-cut 48 of tube 42 from receding from the plane of the cut ends of the wires 41, either at the time the casing is cut into lengths, at the time the end fitting 49 is swaged onto the casing, or after continued use of the casing.

Further assurance of a leak-proof connection between the end fitting 49 and casing 40 is obtained in the provision of a washer 50 which is positioned between the end of the casing and shoulder 51 in fitting 49. The washer is preferably of a flexible material and is Waterproof and water-resistant. By seating the ends of the wires 41 firmly against and into the washer 50, the washer will in turn press tightly against and slightly deform the square cut end 48 of the anchored inner tube 42, increasing the sealing effect between the tube 42 and the end fitting 49.

The annular grooves 52 within the inner end of the end fitting 50 are pressed firmly into the outer covering 53 of the casing to assure an effective seal against the outer elements. It has been found that the most suitable outer covering material is linear polyethylene which in no way hinders the flexibility of the cable and yet provides a tough exterior.

By providing an outer cover 53 (FIG. 6) in which the radially outer convolutions of the wires 41 are embedded,

there are no voids or interstices on the radially outer side of the wires along which water can seep. This becomes especially important in the situation where a portion of the outer cover 53 has been abraded or otherwise damaged so as to expose a portion of the wires 41. In the improved cable, corrosion would be confined to the exposed area. It should be similarly apparent that should the washer 50 be damaged, only the very ends of the wire would be exposed to corrosion since both the radially inner and the radially outer sides of the wires are completely embedded.

The casing may be spooled for bulk sales or cut into lengths and fitted with end fittings.

When the end fittings 49' are swaged into gripping engagement with the wires 41, the wires are forced tightly together as a cylindrical group with the points of contact between the wires being slightly flat. This produces a necking-down of the wires at that point, which provides a very strong joiner of the end fitting to the cable but, at the same time, reduces the inner diameter of tube 42. Before supplying the casing with a core, the reduced internal diameter is reamed to proper size.

In a cable constructed according to the present invention the tube 42 is sufllciently anchored to the casing wire that, even under continued use, the reamed portion does not move longitudinally with respect to the coil of wires. However, in prior art constructions wherein this anchoring was not so effectively accomplished, the end of the tube could retreat in use so that an unreamed thickness of the tube would be positioned at the neck-down portion of the wires. This closed the interior of the tube at that point, gripping the cable core like a lathe collet, with a resultant serious loss of effiicency and, in some cases, a complete lock-up of the core element.

It should be apparent, from the foregoing detailed description of the improved push-pull oable casing and the method of manufacturing the same, that such a casing accomplishes the objects of the invention.

What is claimed is:

1. A push-pull cable casing for receiving a slidable flexible core, comprising, a plurality of helically coiled casing Wires in side-by-side cont act with separation spacings therebetween at random intervals around and along said helical coil, a flexible plastic inner tube extending throughout the length of the coil of casing wires, the radially inner surface of said casing wires being embedded in said plastic inner tube, keys of said inner tube extending through said separation spacings, and a flexible, radial restraining means embracing said casing wires, said plastic inner tube adapted to slidably receive a core engageable therewith and freely movable axially therein, the neutral bending axis of said cable casing being coincident with its geometric center line.

2. A push-pull cable casing for receiving a slid able flexible core, comprising a plurality of dead-straight spring wires helically coiled in side-by-side contact with separation spacings therebetween at random intervals around and along said helical coils, a flexible plastic inner tube extending through the length of the coil of easing wires, the radially inner surface of said casing Wires being embedded in said plastic inner tube, keys of said inner tube extending through said separation spacings and gripped by said wires, a flexible radial restraining means embracing said casing wires, said plastic inner tube adapted to slidably receive a core engageable therewith and freely movable axially therein, the neutral bending axis of said cable casing being coincident with its geometric center line.

3. A push-pull cable casing for receiving a slidable flexible core, comprising a plurality of dead-straight spring wires helically coiled without twisting in side-byside contact with separation spacings therebetween at random intervals around and along said helical coils, a flexible thermoplastic inner tube extending through the length of the coil of easing wires, the radially inner surface of said casing wires being embedded in siad thermoplastic inner tube, keys of said thermoplastic inner tube extending through said separation spacings and gripped by said wires, a flexible radial restraining means embracing said casing wires, said thermoplastic inner tube adapted to slidably receive a core engageable therewith and freely movable axially therein, the neutral bending axis of said cable casing being coincident with its geometric center line.

4. A push-pull cable casing for receiving a slidable flexible core, comprising a plurality of dead-straight spring wires helically coiled in side-by-side contact with separation spacing therebetween at random intervals around and along said helical coils, a flexible plastic inner tube extending through the length of the coil of easing Wires, the radially inner surface of said casing wires being embedded in said plastic inner tube, keys of said inner tube extending through said separation spacings and gripped by said wires, a flexible outer cover embracing the radially outer surface of said casing wires, an end fitting on said cable casing, said fitting having an internal bore for receiving one end of said coiled wire, a shoulder within said bore, the end of said inner tube seated against said shoulder, said plastic inner tube adapted to slidably receive a core engageable therewith and freely movable axially therein, the neutral bending axis of said cable casing being coincident with its geometric center line.

5. A push-pull cable casing 'for receiving a slidable flexible core, comprising a plurality of dead-straight spring wires helical'ly coiled in side-by-side contact with separation spacings therebetween at random intervals around and along said helical coils, a flexible plastic inner tube extending through the length of the coil of casing wires, the radially inner surface of said casing wires being embedded in said plastic inner tube, keys of said inner tube extending through said separation spacings and gripped by said wires, a flexible outer cover embracing the radially outer surface of said casing wires, an end fitting at each end of said cable casing, said fitting saving an internal bore for receiving one end ofsaid coiled wire, a shoulder within said bore, a resilient washer means positioned between said shoulder and the end of the wires in said coil, said wires seated into said resilient washer means, said inner tube sealingly engaging said washer means, said plastic tube adapted to slidably receive a core engageable therewith and freely movable axially therein, the neutral bending axis of said cable casing being coincident with its geometric center line.

References Cited UNITED STATES PATENTS 2,706,494- 4/1955 Morse 74-501 X 2,787,917 4/ 1957 Schroeder 74501 X 3,015-969 1/1962 Bratz -1 642 X 3,063,303 11/1962 Cadwallader 74501 3,130,754 4/1964 Bratz 745(l1 X HALL C. C'OE, Primary Examiner. 

